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Full text of "The manufacture and properties of iron and steel"

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CHAPTER XII.
SPECIAL METHODS OF MANUFACTURE.
SECTION Xlla.—Low-phosphorus acid open-hearth steel at Steel-ton.—The early history of the open-hearth in the United States is confined to the making of acid steel, very little basic metal being made until after 1890. A large proportion of the output went into, boiler plate and quite a quantity into forgings, while there was a considerable tonnage of high-carbon steel. The ordinary grades of boiler steel and forgings were made of stock running from .08 to .10 per cent, of phosphorus, while metal for fireboxes and special forgings, as well as some of the high-carbon steel, was made of low-phosphorus stock, usually a mixture of Swedish pig-iron and charcoal blooms. A certain quantity of low-phosphorus pig-iron was made in America,- and during the latter part of the acid epoch a considerable quantity was manufactured of what is known as "washed metal." This is made by treating melted pig-iron in a furnace lined with iron ore and lime and eliminating most of the "silicon, sulphur and phosphorus and about half the carbon. The pig-iron is the same grade as is used in the basic open-hearth furnace, and the "washed metal" process is essentially the same as the basic open-hearth process of to-day. It differs from it in the following particulars:
(1)   In the basic open-hearth furnace, the bottom is made as durable as possible and it is desired that it shall not be cut away by the action of the metal and slag.   The iron ore needed to oxidize the metalloids and the lime to make a basic slag are both added with the charge, and the reactions take place in a definite way very similar to the fusions made by a chemist in a platinum crucible, the crucible playing no part in the reaction.    In the washed metal process the bottom is not durable, but is intended to supply the ore and lime to oxidize the metalloids and give a basic slag.
(2)   The washed metal furnace is not allowed to reach a very high
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